Funny statistics, I carry 3 around with me depending on the occasion. Never been more then scratched.....

Thinking waving a sharp pointy thing around a criminals face is some how going to descalate the situation is rather moronic at best. Nope if you decide to wave a knife around in a situation as those listed you deserver to be stabbed or worse killed. Use the d*** thing and don't let them see it. If you arent prepared to use a knife or kill someone over that 30$'s in your wallet give it to them and back off. If you arent prepared for what the situation demands then don't walk yourself into that situation.

Knife's, guns, bats, daggers, sharp bottles, pointy sticks don't magically solve the situation. They escalate it and if you arent prepared to use them and reap the inevitable consequences then you shouldnt have been carrying a weapon and putting yourself into that position.

I'm going to somewhat agree with Horetore for once, somewhat. If you arent prepared to kill the person with that knife, it's best to run and not start waving it around. Or better yet throw what they want at them and run.